Yes you can. You can enter a weight to be calculated in kg or lbs, and it'll return the result in whatever mode (kg, lbs, or mixed) you happen to be in.
Changing the mode means restricting the available discs that will be used for calculations. Additionally, you can set whether discs are ever available under preferences. For example, my gym lacks 55 lbs and 15 lbs plates, so I turn those off. The same goes for some of the change kg plates.